Urinary incontinence affects over 13 million men and women of all ages in the United States. Stress urinary incontinence (SUI) affects primarily women and is generally caused by two conditions, intrinsic sphincter deficiency (ISD) and hypermobility. These conditions may occur independently or in combination. In ISD, the urinary sphincter valve, located within the urethra, fails to close properly (coapt), causing urine to leak out of the urethra during stressful activity. Hypermobility is a condition in which the pelvic floor is distended, weakened, or damaged, causing the bladder neck and proximal urethra to rotate and descend in response to increases in intra-abdominal pressure (e.g., due to sneezing, coughing, straining, etc.). The result is that there is an insufficient response time to promote urethral closure and, consequently, urine leakage and/or flow results.
A popular treatment of SUI is the use of a sling, which is permanently placed under a patient's bladder neck or mid-urethra to provide a urethral platform. Placement of the sling limits the endopelvic fascia drop, while providing compression to the urethral sphincter to improve coaptation. Generally, the sling is surgically placed under urethra or bladder neck, close to the high-pressure zone with no elevation of the urethra. When abdominal pressure increases, the sling stops the descent of the urethra and functions as a mechanism of closure for the urethra to prevent urine leakage. However, if too much tension is applied, the patient may go into urine retention, unable to void the bladder and suffer a pressure build-up in the bladder. Such pressure build-up can lead to reflux of urine up the ureters and into the kidney, eventually resulting in kidney damage, and, potentially, kidney loss. If the tension is too small, the implanted sling may not perform its function as intended. Clinically, there is technical challenge to position and apply the correct tension to the sling. Therefore, it is sometimes necessary to modify the sling tension after the implantation surgery of the sling. Currently, there is no easy method to adjust the tension of the sling to compensate for the tension change of the sling over time. Therefore, improved surgically implantable slings, and methods to adjust the sling tension are needed.